I'd say that the US arrive once the word gets out that there's a TF there.

I'd LOVE to see something like a Hercules land, and out of the back rolls a truck, a big blue one that has flames on it.

Chinese Officer:"What's that for?"
Lennox: "Just in case"
Chinese Officer: "In case of what?"
Lennox: (looking over the Officer's shoulder) "THAT.. MOVE MOVE MOVE!"
(we hear the movie transformation sound effect as he runs, and the Decepticon charges Prime, who barrels into it, a la the Animated movie, does a "transform on the turn" and draws a bead on the 'con)
Optimus: "Stand down, there's no need for further violence"